1. Field of the Invention
This invention relates to a digital image data recording apparatus inclusive of a digital video tape recorder (DVTR) and digital camera, etc., a method of recording digital image data in a DVTR, an apparatus and method for reproducing digital image data that has been recorded on a magnetic tape by the DVTR or recording method, as well as a solid-state electronic image sensing device and a method of reading a signal charge out of the solid-state electronic image sensing device.
2. Description of the Related Art
A digital video tape recorder (DVTR) senses the image of a subject using a solid-state electronic image sensing device such as a CCD, converts a video signal, which represents the image of the subject obtained by image sensing, to digital image data and records the digital image data on magnetic tape. A CCD used in a DVTR generally has about 350,000 pixels in an array of 720 pixels horizontally and 480 pixels vertically. A signal charge that accumulates in the solid-state electronic image sensing device used in the DVTR represents the image of the subject. The signal charge can be read out of the device by non-interlaced readout (readout of all pixels) and by interlaced readout (movie readout).
In non-interlaced readout, all of the signal charge that has accumulated in the solid-state electronic image sensing device is outputted at a period of 1/30 of a second. Accordingly, non-interlaced readout makes its possible to obtain a high-quality image of a subject and is a method of readout that is suitable for situations in which the reproduction of still pictures is considered. In interlaced readout, output of signal charge that has accumulated in odd-numbered rows of photoelectric transducers in the solid-state electronic image sensing device and output of signal charge that has accumulated in even-numbered rows of the photoelectric transducers alternate every 1/60 of a second. Interlaced readout makes it possible to shorten the signal-charge output period in comparison with non-interlaced readout and is a method of readout that is suitable for situations in which reproduction of moving pictures is considered.
With non-interlaced readout, one frame is composed of two fields and frame recording for recording a frame image is performed. According to interlaced readout, field recording which records a field image for every field is carried out. In both frame recording and field recording, one frame of image data is recorded on magnetic tape over a time of 1/30 of a second and using a recording area composed of ten tracks.
Thus, in a digital video tape recorder, one frame of image data of the digital image data obtained by photographing a subject using a 350,000-pixel CCD generally is recorded on ten tracks over a period of 1/30 of a second. This recording scheme is the standard in industry (For example, see NIKKEI ELECTRONICS BOOKS, "Data Compression and Digital Modulation", pp. 137.about.152, Nikkei BP Sha, 1993).
The image quality in the image sensing section of the digital video tape recorder depends upon the number of pixels in the CCD; the larger the number of CCD pixels, the greater the improvement in image quality. However, in order for image data obtained from a CCD to be recorded on magnetic tape using a CCD having a large number of pixels for the sake of improving image quality, the recording of the image data requires more than 1/30 of a second and a recording area of more than ten tracks. This is not in conformity with the above-mentioned standard established for a digital video tape recorder.
In a case where the image sensing section of a DVTR uses a CCD having more pixels than the approximately 350,000 pixels employed conventionally, there is a need for interlaced readout and non-interlaced readout suited to such a CCD.